package czk.concrent.juc.semaphore;

import java.sql.*;
import java.util.Map;
import java.util.Properties;
import java.util.concurrent.Executor;
import java.util.concurrent.Semaphore;
import java.util.concurrent.atomic.AtomicIntegerArray;

/**
 * semaphore改进线程池
 * 每次醉倒山歌连接
 * 多线程情况下，线程池的实现
 *
 * @Author:ChenZhangKun
 * @Date: 2020/6/20 20:52
 */
public class OwnDataSourcePoolWithSemaphore {
    public static void main(String[] args) {
        Pool pool = new Pool(50);
        for (int i = 0; i < 10; i++) {
            new Thread(() -> {
                try {
                    Connection borrow = pool.borrow();
                    Thread.sleep(2 * 1000);
                    pool.free(borrow);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }).start();
        }
    }
}

class Pool {
    // 连接池大小
    private final int poolSize;
    // 连接对象的数组
    private Connection[] connections;
    // 连接状态数组 0 表示空闲，1表示繁忙
    private AtomicIntegerArray states;
    // 创建限制线程数
    Semaphore semaphore = new Semaphore(3);

    // 构造方法对属性进行初始化

    public Pool(int poolSize) {
        this.poolSize = poolSize;
        connections = new Connection[poolSize];
        states = new AtomicIntegerArray(new int[poolSize]);
        for (int i = 0; i < poolSize; i++) {
            connections[i] = new MockConnection();
        }
    }

    // 取出连接
    public Connection borrow() {

        // 标记，线程数减少一
        try {
            semaphore.acquire();
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        // 循环遍历数组中是否有空闲连接
        for (int i = 0; i < poolSize; i++) {
            if (states.get(i) == 0) {
                // 将当前的线程的状态置为繁忙,由于有现成安全问题，所有要有cas保护
                if (states.compareAndSet(i, 0, 1)) {
                    System.out.println("获取到连接、开始工作");
                    return connections[i];
                }
            }
        }
        // 永远不会执行到这儿
        return null;

            /*// 此时没有空闲连接，当前线程进入等待状态
            // cas适用于短时间的，此时进入休息室会减少资源开销
            synchronized (this){
                try {
                    // 进入monitor 休息室
                    System.out.println("没有连接，进入wait休息室");
                    this.wait();
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }*/

    }

    // 归还连接
    public void free(Connection connection) {
        for (int i = 0; i < poolSize; i++) {
            // 判断是否是该类型的连接
            if (connection == connections[i]) {
                // 只有线程的持有者才能操作此线程，所以没有线程安全问题
                states.set(i, 0);
                /*synchronized (this) {
                    System.out.println("归还连接，唤醒其他线程");
                    this.notifyAll();
                }*/
                // 线程数加一
                System.out.println("释放连接");
                semaphore.release();
                break;
            }
        }

    }
}

class MockConnection implements Connection {

    @Override
    public Statement createStatement() throws SQLException {
        return null;
    }

    @Override
    public PreparedStatement prepareStatement(String sql) throws SQLException {
        return null;
    }

    @Override
    public CallableStatement prepareCall(String sql) throws SQLException {
        return null;
    }

    @Override
    public String nativeSQL(String sql) throws SQLException {
        return null;
    }

    @Override
    public void setAutoCommit(boolean autoCommit) throws SQLException {

    }

    @Override
    public boolean getAutoCommit() throws SQLException {
        return false;
    }

    @Override
    public void commit() throws SQLException {

    }

    @Override
    public void rollback() throws SQLException {

    }

    @Override
    public void close() throws SQLException {

    }

    @Override
    public boolean isClosed() throws SQLException {
        return false;
    }

    @Override
    public DatabaseMetaData getMetaData() throws SQLException {
        return null;
    }

    @Override
    public void setReadOnly(boolean readOnly) throws SQLException {

    }

    @Override
    public boolean isReadOnly() throws SQLException {
        return false;
    }

    @Override
    public void setCatalog(String catalog) throws SQLException {

    }

    @Override
    public String getCatalog() throws SQLException {
        return null;
    }

    @Override
    public void setTransactionIsolation(int level) throws SQLException {

    }

    @Override
    public int getTransactionIsolation() throws SQLException {
        return 0;
    }

    @Override
    public SQLWarning getWarnings() throws SQLException {
        return null;
    }

    @Override
    public void clearWarnings() throws SQLException {

    }

    @Override
    public Statement createStatement(int resultSetType, int resultSetConcurrency) throws SQLException {
        return null;
    }

    @Override
    public PreparedStatement prepareStatement(String sql, int resultSetType, int resultSetConcurrency) throws SQLException {
        return null;
    }

    @Override
    public CallableStatement prepareCall(String sql, int resultSetType, int resultSetConcurrency) throws SQLException {
        return null;
    }

    @Override
    public Map<String, Class<?>> getTypeMap() throws SQLException {
        return null;
    }

    @Override
    public void setTypeMap(Map<String, Class<?>> map) throws SQLException {

    }

    @Override
    public void setHoldability(int holdability) throws SQLException {

    }

    @Override
    public int getHoldability() throws SQLException {
        return 0;
    }

    @Override
    public Savepoint setSavepoint() throws SQLException {
        return null;
    }

    @Override
    public Savepoint setSavepoint(String name) throws SQLException {
        return null;
    }

    @Override
    public void rollback(Savepoint savepoint) throws SQLException {

    }

    @Override
    public void releaseSavepoint(Savepoint savepoint) throws SQLException {

    }

    @Override
    public Statement createStatement(int resultSetType, int resultSetConcurrency, int resultSetHoldability) throws SQLException {
        return null;
    }

    @Override
    public PreparedStatement prepareStatement(String sql, int resultSetType, int resultSetConcurrency, int resultSetHoldability) throws SQLException {
        return null;
    }

    @Override
    public CallableStatement prepareCall(String sql, int resultSetType, int resultSetConcurrency, int resultSetHoldability) throws SQLException {
        return null;
    }

    @Override
    public PreparedStatement prepareStatement(String sql, int autoGeneratedKeys) throws SQLException {
        return null;
    }

    @Override
    public PreparedStatement prepareStatement(String sql, int[] columnIndexes) throws SQLException {
        return null;
    }

    @Override
    public PreparedStatement prepareStatement(String sql, String[] columnNames) throws SQLException {
        return null;
    }

    @Override
    public Clob createClob() throws SQLException {
        return null;
    }

    @Override
    public Blob createBlob() throws SQLException {
        return null;
    }

    @Override
    public NClob createNClob() throws SQLException {
        return null;
    }

    @Override
    public SQLXML createSQLXML() throws SQLException {
        return null;
    }

    @Override
    public boolean isValid(int timeout) throws SQLException {
        return false;
    }

    @Override
    public void setClientInfo(String name, String value) throws SQLClientInfoException {

    }

    @Override
    public void setClientInfo(Properties properties) throws SQLClientInfoException {

    }

    @Override
    public String getClientInfo(String name) throws SQLException {
        return null;
    }

    @Override
    public Properties getClientInfo() throws SQLException {
        return null;
    }

    @Override
    public Array createArrayOf(String typeName, Object[] elements) throws SQLException {
        return null;
    }

    @Override
    public Struct createStruct(String typeName, Object[] attributes) throws SQLException {
        return null;
    }

    @Override
    public void setSchema(String schema) throws SQLException {

    }

    @Override
    public String getSchema() throws SQLException {
        return null;
    }

    @Override
    public void abort(Executor executor) throws SQLException {

    }

    @Override
    public void setNetworkTimeout(Executor executor, int milliseconds) throws SQLException {

    }

    @Override
    public int getNetworkTimeout() throws SQLException {
        return 0;
    }

    @Override
    public <T> T unwrap(Class<T> iface) throws SQLException {
        return null;
    }

    @Override
    public boolean isWrapperFor(Class<?> iface) throws SQLException {
        return false;
    }
}
